1. Field of the Invention
The present invention relates to an optical transceiver having a light emitting element and a light receiving element.
2. Description of the Related Art
An optical transceiver having a light receiving module and a light transmitting module is used for an optical transmission systems such as data links and optical LANs that use light as an information transmission medium. The light receiving module converts an optical signal transmitted via optical fibers to an electric signal and outputs the electric signal. The light transmitting module converts an electric signal to an optical signal. An optical transceiver in related art is configured as shown in FIG. 22.
An optical transceiver 280 shown in FIG. 22 includes a TO metal package 283, an electronic circuit substrate 281, a resin mold part 282, and lead pins 284. The TO metal package 283 is engaged with an optical connector. The electronic circuit substrate 281 has an electronic circuit for processing an electric signal corresponding to an optical signal transmitted or received to/from the optical connector formed thereon. The resin mold part 282 is used for fixing the TO metal package 283 and the electronic circuit substrate 281. The lead pins 284 are used for connecting the electronic circuit substrate 281 with an external mounting substrate. The light emitting element and light receiving element, not shown in FIG. 22, are housed in the TO metal package 283 and protected from an external electromagnetic noise.
However, in the optical transceiver 280 of the related art, the electronic circuit substrate 281 is extended in a horizontal direction, that is, a direction where a light emitting element and a light receiving element were arranged in parallel to each other. Accordingly, it has not been impossible to narrow the spacing between the light emitting element and the light receiving element. As a result, in the related art, the optical transceiver suffered from a disadvantage that it could not support small-sized optical connectors.
Further, as the optical signal to be transmitted travels at a high speed, over 1 Gbps, the influence of an electromagnetic noise between a light emitting element and a light receiving element or between a driving circuit for the light emitting element and a circuit for the light receiving element becomes serious thus having adverse effects on the receiving sensitivity characteristics.
Accordingly, it is an object to provided a small-sized optical transceiver with a narrower spacing between a light emitting element and a light receiving element and with a structure that can realize stable operation in transmission speeds exceeding 1 Gbps.
An optical transceiver according to the invention comprises a receiver optical sub-module, a transmitter optical sub-module, and a housing to accommodate these modules. The receiver optical sub-module has a light receiving element for receiving an optical signal from a receiver optical fiber and a receiver electronic circuit substrate having an electronic circuit formed thereon. The electronic circuit processes output signals from the light receiving element. The transmitter optical sub-module has a light emitting element to transmit an optical signal to a transmitter optical fiber and a transmitter electronic circuit substrate having an electronic circuit formed thereon. The electronic circuit processes input signals to the light emitting element. The housing has a receptacle part with which an optical connector is engaged that accommodates the receiver optical fiber and the transmitter optical fiber. The receiver optical sub-module and the transmitter optical sub-module are attached to the housing. In this optical transceiver, the receiver electronic circuit substrate and the transmitter electronic circuit substrate are disposed opposite to each other. Preferably, the transmitter electronic circuit substrate may be substantially parallel to the receiver electronic circuit substrate in their longitudinal direction. Further, a surface of the transmitter electronic circuit substrate where the electronic circuit is formed may be substantially parallel to a surface of the receiver electronic circuit substrate where the electronic circuit is formed. The surface of the transmitter electronic circuit substrate where the electronic circuit is formed may be opposite to the surface of the receiver electronic circuit substrate where the electronic circuit is formed. Thus, by arranging the receiver electronic circuit substrate in an opposed position to the transmitter electronic circuit substrate, the receiver electronic circuit substrate and the transmitter electronic circuit substrate can be arranged in the close proximity.
In the optical transceiver, it is preferable that the optical transceiver further comprises an electrical shield plate arranged between the receiver optical sub-module and the transmitter optical sub-module. Thus, by providing an electrical shield plate, it is possible to reduce the effects of an electromagnetic noise mutually generated between the receiver optical sub-module and the transmitter optical sub-module. This electrical shield plate is preferably composed of a conducting plate having a grounding terminal.
In the optical transceiver, it is also preferable that the housing comprises a mounting portion on which the receiver optical sub-module and the transmitter optical sub-module are mounted and a conductive cover for covering the receiver optical sub-module and the transmitter optical sub-module and being coupled to the mounting portion. The cover has a grounding terminal. In this way, by providing a conductive cover to cover the receiver optical sub-module and the transmitter optical sub-module and to have the grounding terminal, it is possible to reduce the effects of an external electromagnetic noise on the receiver optical sub-module and the transmitter optical sub-module.
In the optical transceiver, it is preferable that the receiver optical sub-module further has a metal receiver optical sub assembly, the transmitter optical sub-module further has a metal transmitter optical sub assembly, and the receptacle part is engaged with an optical connector that accommodates the receiver ferrule and the transmitter ferrule. The metal receiver optical sub assembly accommodates a light receiving element therein and has a receiver sleeve for engaging with a receiver ferrule provided at the tip of the receiver optical fiber. The metal transmitter optical sub assembly accommodates a light emitting element and has a transmitter sleeve for engaging with a transmitter ferrule provided at the tip of the transmitter optical fiber.
In the optical transceiver, the receiver optical sub assembly may have a metal stem, a metal lens holder hermetic sealed to the metal stem, and a metal receiver sleeve.
In this way, via a configuration where metal members are combined, alignment of a light receiving element with an optical fiber is made easy and the electromagnetic noise is effectively reduced.
In the optical transceiver, the light receiving element may be mounted on a parallel-plate capacitor installed on the metal stem.
In this way, by mounting the light receiving element on a parallel-plate capacitor, it is possible to reduce the area of the stem and the bypass effect of an electromagnetic noise is provided for a signal whose transmission speed exceeds 1 Gbps.
In the optical transceiver, the receiver optical sub assembly may comprise five external lead pins and connected to a receiver electronic circuit substrate so that the length of the ground lead pin provided in the center of the metal stem may be shortest.
Via such a configuration, it is possible to enhance the resistance against an electromagnetic noise from a high-frequency wave whose transmission speed exceeds 1 Gbps.
In the optical transceiver, the receiver optical sub assembly and the transmitter optical sub assembly preferably have an operating speed equal to or greater than 1.0 Gbps.
In the optical transceiver, the transmitter optical sub assembly may have a metal stem, a metal lens holder hermetic sealed to the metal stem, an aligning member laser welded to the metal lens holder, and a transmitter sleeve laser welded to the aligning member.
Via such a configuration, alignment of a light emitting element with an optical fiber is made easy and light from a light emitting device can be efficiently guided to an optical fiber. Via a configuration where metal members are combined, the electromagnetic noise is effectively reduced.
In the optical transceiver, the transmitter sleeve preferably has a fiber stub, a sleeve for holding the fiber stub, a metal bush for holding the sleeve, and a protective member for holding the bush and the sleeve.
In the optical transceiver, the center of the metal stem may be inclined against the common optical axis connecting the sleeve, fiber stub and lens holder.
Via such a configuration, it is possible to prevent a reflected light coming from the surface of a light receiving device mounted in an inclined face in order to monitor the back light of the light emitting device from returning to the light emitting device again. Thus, it is possible to operate the light emitting device in a high-frequency range.
In the optical transceiver, it is preferable that the metal stem comprises at least three lead pins and that at least one of the lead pins is electrically connected to the metal stem. The transmitter optical sub assembly preferably has an operating speed equal to or greater than 1.0 Gbps
An optical transceiver according to the invention comprises (1) a first opto-electrical conversion device and (2) a housing. The first opto-electrical conversion device can convert one of an optical signal or an electric signal to the other. The housing (2) has (2a) a first receptacle provided to receive an optical connector, (2b) a first shield member for electrically shielding the first receptacle, and (2c) a second shield member for electrically shielding the first opto-electrical conversion device. In this optical transceiver, the first shield member is isolated from the second shield member.
The first shield member for electrically shielding the first receptacle is provided to assure electrical isolation from the second shield member for electrically shielding the first opto-electrical conversion device. Thus it is possible to reduce the electromagnetic effects on the first shield member directly propagated to the second shield member.
Characteristics according to the invention can be arbitrarily combined, and accordingly, each action and each effect and an action and an effect a combination thereof can be provided.
In an optical transceiver according to the invention, the housing (2) may have (2c) an insulating member for electrically insulating the first shield member from the second shield member. Via the insulating member, electrical isolation between the first shield member and the second shield member is assured.
In an optical transceiver according to the invention, the housing (2) may have (2d) a receptacle member where the first receptacle is provided and (2e) a mounting member for mounting the first opto-electrical conversion device. The first shield member may comprise a conductive member provided on the receptacle member. Providing a first shield on the receptacle member serves to reduce a noise radiated from the receptacle. The second shield member may comprise a conductive covering member for sandwiching a first opto-electrical conversion device against a mounting member. Providing the second shield member with a covering member is effective for reducing a radiated noise from the first opto-electrical conversion device.
In an optical transceiver according to the invention, the second shield member may have a terminal provided to stick out from the substrate mounting surface of the housing. This terminal can be used to connect the second shield member to the reference potential line of a mounting member on which the optical transceiver is to be mounted. In an optical transceiver according to the invention, the second shield member may be connected to the reference potential line of a first opto-electrical conversion device. Via this configuration, a stable shield performance is obtained without electrical arrangement of the optical transceiver.
In an optical transceiver according to the invention, the housing (2) may have (2f) a terminal member having conductivity. The terminal member (2f) may have a contact part provided to allow electrical connection to the first shield member and a terminal provided to stick out from the substrate mounting surface of the housing. This terminal member can be used to electrically connect the first shield member to the reference potential line of the cabinet of apparatus for accommodating the optical transceiver.
An optical transceiver according to the invention may further have (3) a second opto-electrical conversion device. The housing (2) has a second receptacle provided to receive (2g) an optical connector. The second opto-electrical conversion device can convert one of an optical signal or an electric signal to the other. The second opto-electrical conversion device is accommodated in the housing so that the second opto-electrical conversion device can be optically connected to the second receptacle. The second receptacle is electrically shielded by the first shield member. The second opto-electrical conversion device is electrically shielded by the second shield member.
Via this embodiment, even in an optical transceiver comprising a plurality of opto-electrical conversion devices, it is possible to reduce the electromagnetic effects on the first shield member for electrically shielding the first receptacle directly propagated to the second shield member for electrically shielding the first opto-electrical conversion device.
In an optical transceiver according to the invention, the first shield member is provided to allow shielding between the first opto-electrical conversion device and the second opto-electrical conversion device. Via this, a radiation noise from the first and the second opto-electrical conversion devices is reduced and a mutual interference between the first and the second opto-electrical conversion devices.
In an optical transceiver according to the invention, the first shield member can comprise a plate coating provided on the receptacle member. Via the conductive coating provided on the receptacle member, a conductive material for shielding can be realized. This embodiment is effective for reducing a radiated noise from the receptacle.